The stretching of light waves to longer, redder wavelengths as observed from objects moving away from us or in strong gravitational fields. This phenomenon provides crucial evidence for the expanding universe.
Coined in the early 20th century from 'red' (referring to the longer wavelength end of the spectrum) and 'shift.' The term gained prominence with Edwin Hubble's observations showing that distant galaxies exhibit redshift proportional to their distance.
Redshift is like cosmic archaeology - the more redshifted a galaxy appears, the further back in time we're seeing it! Some galaxies are so redshifted that their ultraviolet light has been stretched all the way into infrared wavelengths.
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